Tricycle

ABSTRACT

A tricycle includes left and right front wheel support members which rotatably support left and right front wheels, respectively, and which are disposed on laterally opposite sides of a handle post and pivotally supported on left and right leg members which are supported by the handle post, a steering shaft which is connected to the front wheel support members to steer the front wheels in response to the turning operation of the steering shaft, and a driven wheel supported at a rear portion of a vehicle body frame structure. In this tricycle, a banking travel is possible, leading to an enhanced steering travelability. The handle post  21  and the left leg member  29   L  are connected to each other through a pair of left upper and lower links  38   L   , 39   L  to form a left parallel link arrangement  37   L , while the handle post  21  and the right leg member  29   R  are connected to each other through a pair of right upper and lower links  38   R   , 39   R  to form a right parallel link arrangement  37   R   , 94   R . The left and right parallel link arrangements  37   L   , 37   R  are formed laterally symmetrically with each other with respect to the handle post  21.

FIELD OF THE INVENTION

The present invention relates to a tricycle including a pair of left andright front steerable wheels supported at a front portion of a vehiclebody frame structure, and a single rear drivable wheel supported at arear portion of the vehicle body frame structure, and particularly, toan improvement in a tricycle which can travel on a banking in anattitude in which the vehicle body frame structure is inclined inleftward and rightward directions along with the left and right frontwheels.

The terms “left” and “right” used in this specification mean the leftand right in a state in which the vehicle body frame structure is turnedforwards in an advancing direction of the tricycle.

PRIOR ART

Tricycles which are travelable on bankings are disclosed in, forexample, Japanese Patent Application Laid-open Nos. 6-171569, 56-82681and 1-229787.

In the tricycles disclosed in Japanese Patent Application Laid-open Nos.6-171569 and 56-82681, the left and right front wheels are disposed tooverhang largely from the turning axis. For this reason, it is extremelydifficult to enhance the rigidity of support of the front wheels, whileproviding a reduction in weight of each portion or component, and if therigidity of support is insufficient, it particularly results in lack ofa stability in the banking travel. If the amount of overhanging of theleft and right front wheels from the turning axis is large, an inertiamoment of the steering system is increased, thereby making it difficultto carry out a light steering operation.

In the tricycle disclosed in Japanese Patent Application Laid-open No.1-229787, the left and right front wheels are disposed on the turningaxis, but a large number of expensive ball joints are used to supportthe front wheels in such a disposition. This brings about a reduction inrigidity of support of each of the front wheels, and makes it difficultto reduce the cost.

The present invention has been accomplished with such circumstances inview, and it is an object of the present invention to provide aninexpensive tricycle, wherein the rigidity of support of the left andright front wheels is high enough to enable banking travel, even ifexpensive ball joints are not used, and moreover, the steering operationcan be conducted lightly.

DISCLOSURE OF THE INVENTION

To achieve the above object, according to a first aspect and feature ofthe present invention, there is provided a tricycle including a pair ofleft and right front steerable wheels supported at a front portion of avehicle body frame structure, and a single rear drivable wheel supportedat a rear portion of the vehicle body frame structure, wherein thetricycle comprises a cylindrical handle post which is fixedly mounted ata front end of the vehicle body frame structure and which turnablysupports a steering shaft connected to a steering handlebar, left andright upper links which are integrally connected to each other andpivotally supported at an upper end of the handle post, left and rightlower links which are integrally connected to each other and pivotallysupported at a lower end of the handle post, a cylindrical left legmember which is pivotally supported at upper and lower opposite endsthereof to outer ends of the left upper and lower links, a cylindricalright leg member which is pivotally supported at upper and loweropposite ends thereof to outer ends of the right upper and lower links,a left front wheel support member rotatably supported on the left legmember, a right front wheel support member rotatably supported on theright leg member, the left front wheel being supported on the left frontwheel support member and disposed immediately below the left leg member,the right front wheel being supported on the right front wheel supportmember and disposed immediately below the right leg member, and asteering operatively-connecting means being disposed below the handlepost and both the leg members for operatively connecting the steeringshaft and the left and right front wheel support members to each other.

According to a second aspect and feature of the present invention, thereis provided a tricycle including a pair of left and right frontsteerable wheels supported at a front portion of a vehicle body framestructure, and a single rear drivable wheel supported at a rear portionof the vehicle body frame structure, wherein the tricycle comprises acylindrical handle post which is fixedly mounted at a front end of thevehicle body frame structure and which turnably supports a steeringshaft connected to a steering handlebar, left and right upper linkswhich are independent from each other and pivotally supported at anupper end of the handle post, left and right lower links which areindependent from each other and pivotally supported at a lower end ofthe handle post, a cylindrical left leg member which is pivotallysupported at upper and lower opposite ends thereof to outer ends of theleft upper and lower links, a cylindrical right leg member which ispivotally supported at upper and lower opposite ends thereof to outerends of the right upper and lower links, a left front wheel supportmember turnably supported on the left leg member, a right front wheelsupport member turnably supported on the right leg member, left andright connecting frames which are fixedly mounted on at least ones of:the left and right upper links; and the left and right lower links,respectively, a connecting member which is turnably connected atopposite ends thereof to the connecting frames, the left front wheelbeing supported on the left front wheel support member and disposedimmediately below the left leg member, the right front wheel beingsupported on the right front wheel support member and disposedimmediately below the right leg member, and a steeringoperatively-connecting means being disposed below the handle post andboth the leg members for operatively connecting the steering shaft andthe left and right front wheel support members to each other.

The steering operatively-connecting means in each of the first andsecond features corresponds to a pit-man arm 31, a knuckle arm 32, a tierod 33 and a ball joint 34 in embodiments of the present invention whichwill be described later.

With the first and second features, the left and right cylindrical legmembers are pivotally supported at upper and lower opposite ends thereofby the left and right upper and lower links, and the left and rightfront wheels disposed immediately below the left and right leg membersare supported by the left and right front wheel support members whichare rotatably supported on the left and right leg members. Therefore,the left and right front wheels do not overhang sideways of the left andright leg members and hence, the rigidity of support of the left andright front wheels can be enhanced effectively in cooperation with thefirm supporting of the upper and lower opposite ends of the leg members.As a result, it is possible to provide an enhancement in stability ofthe banking travel.

In addition, because the left and right front wheels do not overhangsideways of the left and right leg members, a reduction in inertiamoment of the steering system is brought about, whereby the steeringoperation can be conducted lightly.

Further, since the steering operatively-connecting means for operativelyconnecting the steering shaft and the left and right front wheel supportmembers to each other is disposed below the handle post and the left andright leg members, a wide space, which is free from interference of thesteering operatively-connecting means, can be ensured in front of andabove the handle post and the left and right leg members and hence, itis easy to place a carrier and the like.

Moreover, no ball joint is used in order to support the left and rightfront wheels, as described above, and hence, it is easy to ensure therigidity of support of the front wheels, and it is possible to provide areduction in cost.

According to a third aspect and feature of the present invention, inaddition to the first or second feature, a left upright attitudemaintaining means is provided between the handle post and one of theleft upper and right links for exhibiting a spring force for returningthe handle post to upright attitude thereof in response to the handlepost inclining leftwards from the upright attitude, but for avoidingexhibiting a spring force, when the handle post is inclined rightwardsfrom the upright attitude, and a right upright attitude maintainingmeans is provided between the handle post and one of the right upper andlower links for exhibiting a spring force for returning the handle postto upright attitude thereof in response to the handle post incliningrightwards from the upright attitude, but for avoiding exhibiting aspring force, when the handle post is inclined leftwards from theupright attitude, and a spring force for biasing the handle post in adirection toward the upright attitude being applied to the left andright upright attitude maintaining means even in the upright state ofthe handle post.

With the third feature, when the vehicle body frame structure has beeninclined leftwards, a spring force for returning the vehicle body framestructure toward the upright attitude is applied to the vehicle bodyframe structure by the left upright attitude maintaining means. When thevehicle body frame structure has been inclined rightwards, a springforce for returning the vehicle body frame structure toward the uprightattitude is applied to the vehicle body frame structure by the rightupright attitude maintaining means. When the tricycle is at a stop in anon-ridden state, a driver can ride on the tricycle without anxiety inthe upright attitude of the vehicle body frame structure. When thetricycle has been switched over from a turning traveling state with thevehicle body frame structure inclined, to a straight traveling state,the vehicle body frame structure is restored to the upright attitude,whereby the steerability can be further enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a tricycle used also as a cart, which is in abicycle mode according to a first embodiment;

FIG. 2 is a side view of a tricycle used also as a cart, which is in acart mode;

FIG. 3 is an enlarged plan view taken in the direction of an arrow 3 inFIG. 1;

FIG. 4 is an enlarged sectional view taken along a line 4—4 in FIG. 1;

FIG. 5 is an enlarged front view taken in the direction of an arrow 5 inFIG. 1 with a carrier omitted;

FIG. 6 is an enlarged sectional view taken along a line 6—6 in FIG. 5;

FIG. 7 is a front view similar to FIG. 5, but with a vehicle body framestructure inclined leftwards;

FIG. 8 is an enlarged sectional view taken along a line 8—8 in FIG. 1;

FIG. 9 is a sectional view taken along a line 9—9 in FIG. 8;

FIG. 10 is a sectional view taken along a line 10—10 in FIG. 9;

FIG. 11 is a side view of a tricycle used also as a cart, which is abicycle mode, according to a second embodiment;

FIG. 12 is a front view taken in the direction of an arrow 12 in FIG.11;

FIG. 13 is an enlarged view of an essential portion shown in FIG. 12;

FIG. 14 is an enlarged sectional view taken along a line 14—14 in FIG.13;

FIG. 15 is a front view similar to FIG. 12, but with the vehicle bodyframe structure inclined leftwards;

FIG. 16 is a side view of a tricycle used also as a cart, which is in abicycle mode, according to a third embodiment;

FIG. 17 is a side view of the tricycle used also as a cart, which is ina cart mode;

FIG. 18 is a side view of a tricycle used also as a cart, which is in abicycle mode, according to a fourth embodiment;

FIG. 19 is an enlarged view of an essential portion shown in FIG. 18;and

FIG. 20 is an enlarged perspective view of an operating lever.

BEST MODE FOR CARRYING OUT THE INVENTION

A mode for carrying out the present invention will now be described byway of embodiments shown in the accompanying drawings.

FIGS. 1 to 10 show a first embodiment of the present invention.

Referring first to FIGS. 1 to 5, a vehicle body frame structure F₁ of atricycle that can be used also as a cart is comprised of a handle post21, a saddle post 22, a rear frame 23, a bottom pipe 24, a first linkpipe 25 and a second link pipe 26. The vehicle body frame structure F₁is capable of being switched over between a bicycle mode in which it hasbeen deployed, as shown in FIG. 1, and a cart mode in which it has beenfolded up, as shown in FIG. 2.

A steering shaft 27 is turnably carried in the handle post 21 extendingupwards and downwards and fitted in the handle post 21, and a steeringhandle bar 28 is fixedly mounted at an upper end of the steering shaft27.

Left and right cylindrical leg members 29 _(L) and 29 _(R) are disposedon left and right opposite sides of the handle post 21 to extend upwardsand downwards in parallel to the handle post 21. A left front wheelsupporting member 30 _(L) supporting a left front wheel W_(FL) forrotating movement is rotatably carried on the left leg member 29 _(L),and a right front wheel supporting member 30 _(R) supporting a rightfront wheel W_(FR) for rotating movement is rotatably carried on theright leg member 29 _(R). In this case, the left front wheel W_(FL) isdisposed immediately below the left leg member 29 _(L), and the rightfront wheel W_(FR) is disposed immediately below the right leg member 29_(R).

A pit-man arm 31 is secured to a lower end of the steering shaft 27below a lower end of the handle post 21, and knuckle arms 32, 32 aresecured to the left and right front wheel supporting members 30 _(L) and30 _(R) below lower ends of the left and right leg members 29 _(L) and29 _(R), respectively. Opposite ends of tie rods 33, 33 are connected tothe pit-man arm 31 and the knuckle arms 32, 32 through ball joints 34,34.

Thus, the pit-man arm 31 is turned leftwards and rightwards through thesteering shaft 27 in response to the turning of the steering handle bar28 in left and right directions, and in response to this, the left andright knuckle arms 32, 32 are turned leftwards and rightwards throughthe tie rods 33, 33, whereby the left front wheel W_(FL) and the rightfront wheel W_(FR) are turned leftwards and rightwards.

A mounting stay 35 is secured to an intermediate portion of the handlepost 21 to protrude forwards, and a carrier 36 is attached to themounting stay 35. It is desirable that the carrier 36 is formed so thatit can be switched over between a service state in which it hasprotruded forwards (a state shown by a solid line in FIG. 1) and in anon-service state in which it has been folded up rearwards (a stateshown by a dashed line in FIG. 1).

The handle post 21 and the left leg member 29 _(L) are connected to eachother through a left upper link 38 _(L) and left lower links 39 _(L) and39 _(L) to form a left parallel link arrangement 37 _(L), and the handlepost 21 and the right leg member 29 _(R) are connected to each otherthrough a right upper link 38 _(R) and right lower links 39 _(R) and 39_(R) to form a right parallel link arrangement 37 _(R). The left andright parallel link arrangements 37 _(L) and 37 _(R) are formedlaterally symmetrically with respect to the handle post 21.

The left and right upper links 38 _(L) and 38 _(R) are each formedintegrally with each other into a pipe-shape and disposed in front ofthe handle post 21 and the leg members 29 _(L) and 29 _(R). The upperlinks 38 _(L) and 38 _(R) are turnably connected at their connections tothe handle post 21 through a connecting pin 40 having an axis extendinglongitudinally. In addition, the left and right upper links 38 _(L) and38 _(R) are turnably connected at their outer ends to upper portions ofthe leg members 29 _(L) and 29 _(R) through connecting pins 41, 41having axes parallel to the connecting pin 40.

The left and right lower links 39 _(L), 39 _(R); 39 _(L), 39 _(R) arealso each formed integrally with each other into a pipe-shape anddisposed at locations in which they sandwich the handle post 21 and theleg members 29 _(L) and 29 _(R) from the front and the rear. The leftand right lower links 39 _(L), 39 _(R); 39 _(L), 39 _(R) are turnablyconnected at their connections to the handle post 21 through connectingpins 42, 42 having axes parallel to the connecting pin 40, and are alsoturnably connected at their outer ends to lower portions of the legmembers 29 _(L) and 29 _(R) through connecting pins 43, 43 having axesparallel to the connecting pins 42, 42, respectively.

In the left parallel link arrangement 37 _(L), a left upright attitudemaintaining means 44 _(L) is provided between the handle post 21 and oneof the left upper and lower links 38 _(L) and 39 _(L), 39 _(L), e.g.,the left lower links 39 _(L), 39 _(L). In the right parallel linkarrangement 37 _(R), a right upright attitude maintaining means 44 _(R)is provided between the handle post 21 and one of the right upper andlower links 38 _(R) and 39 _(R), 39 _(R), e.g., the right lower links 39_(R), 39 _(R).

Referring to FIG. 6, the left upright attitude maintaining means 44 _(L)includes a support shaft 46 mounted between bracket plates 45, 45secured respectively to the left lower links 39 _(L) and 39 _(L) andhaving an axis parallel to the connecting pins 40 to 43 of the leftparallel link arrangement 37 _(L), a guide rod 47 extending upwards anddownwards and turnably carried at its lower end on the support shaft 46,a movable tube 48 coaxially surrounding the guide rod 47, a stationaryretainer 49 disposed between the left lower links 39 _(L), 39 _(L) andsecured to a lower portion of the guide rod 47, a movable retainer 50secured to the movable tube 48, a coil spring 51 mounted undercompression between the stationary retainer 49 and the movable retainer50 to surround the guide rod 47, and an abutment plate 52 fixed to thehandle post 21, so that it can be put into abutment against an upper endof the movable tube 48.

A support tube 53 is secured to the handle post 21 in an intermediateportion between the upper and lower links 38 _(L) and 39 _(L), 39 _(L)of the left parallel link arrangement 37 _(L) and extends toward theleft leg member 29 _(L), and the abutment plate 52 is secured to a tipend of the support tube 53. The abutment plate 52 is provided with aguide bore 54 through which the guide rod 47 is movably inserted, withan upper end of the guide rod 47 being passed through the abutment plate52 to protrude upwards.

An inward-facing collar 55 protruding radially inwards is secured to aninner surface of a lower end of the movable tube 48 to surround theguide rod 47. A limiting collar 56 protruding radially outwards issecured to the guide rod 47 with its outer periphery brought intosliding contact with the inner surface of the movable tube 48, so thatit can be put into abutment against an upper surface of theinward-facing collar 55. Moreover, a limiting collar 56 is secured tothe guide rod 47 in such a manner that the inward-facing collar 55 ofthe movable tube 48 biased upwards by the coil spring 51 is put againstthe limiting collar 56 in a state in which the handle post 21 assumes anupright attitude. In this case, the axial length of the movable tube 48as well as the position of securing of the inward-facing collar 55 tothe movable tube 48 are determined, so that the upper end of the movabletube 48 is in abutment against the lower surface of the abutment plate52, or is at a location extremely close to the lower surface of theabutment plate 52.

A nut 57 is threadedly fitted over the lower portion of the guide rod47, so that its advanced and retreated positions can be regulated. Anend of downward movement of the movable tube 48 is defined by abutmentof the inward-facing collar 55 against the nut 57.

The leg members 29 _(L) and 29 _(R) are also inclined leftwards inresponse to the leftward inclination of the handle post 21, as shown inFIG. 7, because the left and right parallel link arrangements 37 _(L)and 37 _(R) are formed between the handle post 21 and the left and rightleg members 29 _(L) and 29 _(R). In this case, in the left uprightattitude maintaining means 44 _(L), the movable tube 48 is pusheddownwards by the abutment plate 52, while compressing the coil spring51, and a spring force of returning the handle post 21 to its uprightattitude is applied to the abutment plate 52, i.e., to the handle post21. On the other hand, when the handle post 21 is tilted rightwards fromthe upright attitude, an upper limit position of the movable tube 48 isdefined by abutment of the inward-facing collar 55 against the limitingcollar 56. Therefore, the abutment plate 52 is moved away from the upperend of the movable tube 48 and inclined rightwards and hence, a springforce cannot be applied from the left upright attitude maintaining means44 _(L) to the handle post 21.

The right upright attitude maintaining means 44 _(R) basically has thesame structure as the left upright attitude maintaining means 44 _(L),and the detailed description thereof is omitted. The right uprightattitude maintaining means 44 _(R) exhibits a spring force for returningthe handle post 21 to the upright attitude in response to the rightwardtilting movement of the handle post 21 from the upright attitude, butwhen the handle post 21 is tilted leftwards from the upright attitude,the spring force cannot be applied from the right upright attitudemaintaining means 44 _(R) to the handle post 21.

Referring also to FIGS. 8 and 9, the rear frame 23 comprises a pair offrame plates 60, 60 parallel to each other, a tube 61 which has an axisparallel to rotational axes of the left and right front wheels W_(FL)and W_(FR) and which has opposite outer ends protruding outwards fromthe frame plates 60, 60 and connects the frame plates 60, 60 to eachother, and a pair of left and right pipe-shaped rear forks 62, 62secured to the frame plates 60, 60 and the tube 61. When the vehiclebody frame structure F₁ is in the bicycle mode, as shown in FIG. 1, therear forks 62, 62 are inclined rearwards and downwards from the frameplates 60, 60 and the tube 61 to extend rearwards, and the rear wheelW_(R), which is a driven wheel, is pivotally supported at rear ends ofthe rear forks 62, 62.

A crankshaft 64 is rotatably carried in the tube 61 through a ballbearing 63, and crank pedals 65, 65 are fixed to opposite ends of thecrankshaft 64. Moreover, a driving sprocket 66 is fixed to thecrankshaft 64 on the right of the tube 61, and an endless chain 68 isreeved around a follower sprocket 67 fixed to the rear wheel W_(R) andaround the driving sprocket 66. Therefore, the rear wheel W_(R) isrotated by the depression of the crank pedals 65, 65.

The saddle post 22 extends upwards from the rear frame 23 and isturnably connected at its lower end to the rear frame 23 through a pivot(a bolt in this embodiment) 69 which is mounted between both the frameplates 60, 60 and has an axis parallel to the crankshaft 64. A saddle 70is mounted at an upper end of the saddle post 22.

The bottom pipe 24 connects the lower portion of the handle post 21 andthe rear frame 23 to each other. The bottom pipe 24 is turnablyconnected at its one end to a bracket 71 mounted at the lower portion ofthe handle post 21 through a pivot 72 having an axis parallel to thepivot 69, and is turnably connected at the other end to the rear frame23 through a pivot (a bolt in this embodiment) 73 which is mountedbetween both the frame plates 60, 60 and has an axis parallel to thepivot 72.

The first link pipe 25 connects an intermediate portion in the upwardand downward direction of the saddle post 22 and a lengthwiseintermediate portion of the bottom pipe 24 to each other. The first linkpipe 25 is connected at its one end to a bracket 74 secured theintermediate portion in the upward and downward direction of the saddlepost 22 through a pivot (a bolt in this embodiment) 75 having an axisparallel to the pivots 69, 72 and 73, and is connected at the other endto a bracket 76 secured to the lengthwise intermediate portion of thebottom pipe 24 through a pivot (a bolt in this embodiment) 77 having anaxis parallel to the pivot 75.

The second link pipe 26 connects an intermediate portion in the upwardand downward direction of the handle post 21 and a lengthwiseintermediate portion of the first link pipe 25 to each other. The secondlink pipe 26 is connected at its one end to a bracket 78 secured to theintermediate portion in the upward and downward direction of the handlepost 21 through a pivot 79 having an axis parallel to the pivots 69, 72,73, 75 and 77, and is connected at the other end to a bracket 80 securedto the lengthwise intermediate portion of the first link pipe 25 througha pivot (a bolt in this embodiment) 81 having an axis parallel to thepivot 79.

The handle post 21, the saddle post 22, the rear frame 23, the bottompipe 24, the first link pipe 25 and the second link pipe 26, which areturnably connected to one another through the pivots 69, 72, 73, 75, 77,79 and 81 and form the vehicle body frame structure F₁ in the abovemanner, comprise a link mechanism which is capable of switching over,from one to another, a bicycle mode In which the vehicle body framestructure F₁ has been deployed, so that both the left and right frontwheels W_(FL) and W_(FR) and the rear wheel W_(R) are grounded toprovide a maximum wheel base, as shown in FIG. 1, and a cart mode inwhich the vehicle body frame structure F₁ has been folded up, so thatthe rear wheel W_(R) spaced apart from the ground surface is insertedbetween the left and right front wheels W_(FL) and W_(FR) which are intheir grounded states, as shown in FIG. 2.

To facilitate the operation of switching over the bicycle mode and thecart mode from one to the other, a grip 82 is provided at the upper endof the saddle post 22 to protrude rearwards of the saddle 70.

When the vehicle body frame structure F₁ is in the cart mode, the cartmode can be maintained, if the steering shaft 27 and the saddle post 22are fastened by a fastening means 83 such as a rubber band and a stringmember, as shown by a dashed line in FIG. 2. When the vehicle body framestructure F₁ is in the bicycle mode, the bicycle mode of the vehiclebody frame structure F₁ can be maintained by a lock means 84.

The lock means 84 is provided between the saddle post 22 and the rearframe 23 among the handle post 21, the saddle post 22, the rear frame23, the bottom pipe 24, the first link pipe 25 and the second link pipe26 which form the vehicle body frame structure F₁.

The lock means 84 includes a resilient member 85 which is made of anelastic material such as a rubber and which is fixed to the rear frame23 and sandwiched between the saddle post 22 and the rear frame 23 insuch a manner to exhibit a resilient force opposing a riding loadapplied from the saddle post 22 when the vehicle body frame structure F₁is in the bicycle mode, and an engage member 86 which is mounted to therear frame 23 to releasably engage the saddle post 22 to maintain therelative positions of the saddle post 22 and the rear frame 23.

Referring also to FIG. 10, a support plate 87 is secured between boththe frame plates 60, 60 in the rear frame 23 to oppose the rear surfaceof the saddle post 22, when the vehicle body frame structure F₁ has beenbrought into the bicycle mode. The resilient member 85 is secured to thesupport plate 87, so that its abutment surface 85 a recessed in anarcuate shape in correspondence to the rear surface of the pipe-shapedsaddle post 22 faces toward the saddle post 22. Thus, when the vehiclebody frame structure F₁ has been brought into the bicycle mode, theresilient member 85 is sandwiched between the support plate 87 securedto the rear frame 23 and the saddle post 22 and exhibits the resilientforce opposing the riding load applied from the saddle post 22.Moreover, the resilient force exhibited by the resilient member 85 isapplied to the saddle post 22 in a direction to turn the saddle post 22forwards about the axis of the pivot 69 and also applied to the rearframe 23 in a direction to turn the rear frame 23 rearwards about theaxis of the pivot 73. The resilient force exhibited by the resilientmember 85 is applied to the saddle post 22 and the rear frame 23 toprovide the cart mode.

The engage member 86 is turnably support at its base portion by a shaft88 which is provided to extend between both the frame plates 60, 60 andhas an axis parallel to the crankshaft 64. The engage member 86 has ahook-shaped engage claw 86a provided at its tip end. On the other hand,a substantially U-shaped locking member 91 is secured to the saddle post22, so that the engage claw 86 a can be brought into engagement with thelocking member 91. When the vehicle body frame structure F₁ is in thebicycle mode, the relative positions of the saddle post 22 and the rearframe 23 are maintained by bringing the engage claw 86 a into engagementwith the locking member 91, while compressing the resilient member 85.

A torsion spring 89 is mounted between the engage member 86 and areceiving plate 90 secured to an inner surface of one of the frameplates 60, 60 to surround the shaft 88, so that the engage member 86 isbiased and turned by a spring force of the torsion spring 89 in adirection to bring the engage claw 86a into engagement with the lockingmember 91.

Further, an operating portion 86 b is integrally provided at the baseportion of the engage member 86 to protrude outwards in a radialdirection of the shaft 86. Thus, the engage member 86 can be operated ina direction to disengage the engage claw 86 a from the locking member 91by putting an operator's finger onto the operating portion 86 b tooperate the latter.

The operation of the first embodiment will be described below. If thevehicle body frame structure F₁ is deployed into the bicycle mode, asshown in FIG. 1, the tricycle used also as a cart can be used as abicycle. In this case, when the vehicle body frame structure F₁ has beendeployed into the bicycle mode, the locking means 84 is provided betweenthe saddle post 22 and the rear frame 23 among the handle post 21, thesaddle post 22, the rear frame 23, the bottom pipe 24, the first linkpipe 25 and the second link pipe 26 which form the vehicle body framestructure F₁, and the relative positions of the saddle post 22 and therear frame 23 are maintained by the locking means 84, whereby thebicycle mode of the vehicle body frame structure F₁ is maintained.

Moreover, the locking means 84 includes the resilient member 85 which issandwiched between the saddle post 22 and the rear frame 23 and exhibitsthe resilient force opposing the riding load. Even if the fabricatingaccuracy and assembling accuracy for the handle post 21, the saddle post22, the rear frame 23, the bottom pipe 24, the first link pipe 25 andthe second link pipe 26 are somewhat poor, it is possible to absorb thefabricating and assembling errors of the handle post 21, the saddle post22, the rear frame 23, the bottom pipe 24, the first link pipe 25 andthe second link pipe 26 by the resilient member 85 to prevent thelooseness from occurring among the handle post 21, the saddle post 22,the rear frame 23, the bottom pipe 24, the first link pipe 25 and thesecond link pipe 26, thereby enhancing the riding comfort. In addition,it is possible to enhance the cushion property by exhibiting theresilient force opposing the riding load by the resilient member 85,thereby further enhancing the riding comfort.

The left and right parallel link arrangements 37 _(L) and 37 _(R) areformed between the handle post 21 and the left and right leg members 29_(L) and 29 _(R) and hence, the leg members 29 _(L) and 29 _(R) areinclined leftwards and rightwards in response to the leftward andrightward inclination of the handle post 21, whereby the left and rightfront wheels W_(FL) and W_(FR) can be inclined. Thus, a banking travelof the tricycle is feasible, i.e., the tricycle can be allowed to travelwith the vehicle body frame structure F₁ inclined leftwards orrightwards, leading to an enhanced steering travelability.

Moreover, the left and right upper links 38 _(L) and 38 _(R) in theparallel link arrangements 37 _(L) 37 _(R) are formed integrally witheach other, and the left and right lower links 39 _(L), 39 _(L) and 39_(R), 39 _(R) in the parallel link arrangements 37 _(L) and 37 _(R) arealso formed integrally with each other. Therefore, it is possible toreduce the number of parts forming the left and right parallel linkarrangements 37 _(L) and 37 _(R) as much as possible and to reduce thenumber of assembling steps.

Further, in the left parallel link arrangement 37 _(L), the left uprightattitude maintaining means 44 _(L) is provided between the handle post21 and the left lower links 39 _(L) and 39 _(L) for exhibiting thespring force for returning the handle post 21 to the upright attitude inresponse to the leftward inclination of the handle post 21 from theupright attitude, but for avoiding exhibiting a spring force, when thehandle post 21 is inclined rightwards from the upright attitude. In theright parallel link arrangement 37 _(R), the right upright attitudemaintaining means 44 _(R) is provided between the handle post 21 and theright lower links 39 _(R) and 39 _(R) for exhibiting the spring forcefor returning the handle post 21 to the upright attitude in response tothe rightward inclination of the handle post 21 from the uprightattitude, but for avoiding exhibiting a spring force, when the handlepost 21 is inclined leftwards from the upright attitude. Therefore, whenthe vehicle body frame structure F₁ has been inclined either leftwardsor rightwards, the spring force for returning the handle post 21 to theupright attitude is applied to the vehicle body frame structure F₁.Thus, when the tricycle is at stop in a non-ridden state, the vehiclebody frame structure F₁ can be brought into the upright attitude,whereby a driver can ride on the tricycle without anxiety. When thetricycle is switched over from the turning traveling state with thevehicle body frame structure F₁ inclined to a straight traveling state,the vehicle body frame structure F₁ is restored to the upright attitude,whereby the steerability can be further enhanced.

Particularly, the left and right cylindrical leg members 29 _(L) and 29_(R) are pivotally supported at their upper and lower ends by the leftand right upper and lower links 38 _(L), 38 _(R) and 39 _(L), 39 _(R),and the left and right front wheels W_(FL) and W_(FR) disposedimmediately below the left and right leg members 29 _(L) and 29 _(R) aresupported by the left and right front wheel support members 30 _(L) and30 _(R) rotatably carried on the left and right leg members 29 _(L) and29 _(R). Therefore, the left and right front wheels W_(FL) and W_(FR) donot overhang sideways of the leg members 29 _(L) and 29 _(R), and hence,the support rigidity of the left and right front wheels W_(FL) andW_(FR) is enhanced effectively in cooperation with the firm supportingof the upper and lower opposite ends of the leg members 29 _(L) and 29_(R) and as a result, the stability of the banking travel can beenhanced.

In addition, since the left and right front wheels W_(FL) and W_(FR) donot overhang sideways of the leg members 29 _(L) and 29 _(R), areduction in inertia moment of the steering system is provided, wherebythe steering can be carried out lightly.

Further, the steering operatively-connecting means for operativelyconnecting the steering shaft 27 and the left and right front wheelsupport members 30 _(L) and 30 _(R) to each other, i.e., the pit-man arm31, the knuckle arm 32, the tie rod 33 and the ball joint 34 aredisposed below the handle post 21 and the left and right leg members 29_(L) and 29 _(R). Therefore, wide spaces, which are free from theinterference of the steering operatively-connecting means, can beensured in front of and above the handle post 21 and the left and rightleg members 29 _(L) and 29 _(R), whereby it is easy to place the carrier36 and the like.

Moreover, the ball joint is not used in order to support the left andright front wheels W_(FL) and W_(FR), as described above, and hence, itis easy to ensure the support rigidity of the front wheels W_(FL) andW_(FR) and to provide a reduction in cost.

When the tricycle used also as the cart is used as a two-wheel cart, therelative position locking state of the saddle post 22 and the rear frame23 by the locking means 84 may be released in the state in which thevehicle body frame structure F₁ is in the bicycle mode, and the grip 82may be grasped to fold up the vehicle body frame structure F₁.

In this case, the resilient member 85 of the locking means 84 exhibitsthe spring force for biasing the saddle post 22 and the rear frame 23 inthe direction to provide the cart mode, as described above and hence,when the engage member 86 has been turned by the operating portion 86 bto release the maintaining of the relative positions of the saddle post22 and the rear frame 23, the saddle post 22 and the rear frame 23 arebiased in the direction to provide the cart mode by the resilient forceof the resilient member 85, thereby facilitating the operation forswitching over the tricycle from the bicycle mode to the cart mode.

In the sate in which the vehicle body frame F₁ has been folded up intothe cart mode, the rear wheel W_(R) is spaced apart from the groundsurface and inserted between the left and right front wheels W_(FL) andW_(FR) which are in the grounded states and hence, the tricycle usedalso as the cart can be used as the two-wheel cart. In this case, therear wheel W_(R) spaced apart from the ground surface cannot be drivenfrom the ground surface with the movement of cart, and hence, the crankpedals 65, 65 cannot be rotated. Therefore, the cart can be moved freelyion the forward and rearward directions without being obstructed by thecrank pedals 65, 65.

FIGS. 11 to 15 show a second embodiment of the present invention.

Referring first to FIGS. 11 and 12, a handle post 21 and a left legmember 29 _(L) are connected to each other through a pipe-shaped leftupper link 95 _(L) and a pipe-shaped left lower link 96 _(L) to form aleft parallel link arrangement 94 _(L), and the handle post 21 and aright leg member 29 _(R) are connected to each other through apipe-shaped right upper link 95 _(R) and a pipe-shaped right lower link96 _(R) to form a right parallel link arrangement 94 _(R). The left andright parallel link arrangements 94 _(L) and 94 _(R) are formedlaterally symmetrically with respect to the handle post 21.

A pair of upper support plates 97 are secured to an upper portion of thehandle post 21 and extend laterally with the handle post 21 sandwichedtherebetween from the front and the rear, and a pair of lower supportplates 98 are secured to a lower portion of the handle post 21 andextend laterally with the handle post 21 sandwiched therebetween fromthe front and the rear. Upper brackets 99 _(L) and 99 _(R) are securedto the left and right leg members 29 _(L) and 29 _(R) in correspondenceto the upper support plates 97, and lower brackets 100 _(L) and 100 _(R)are also secured to the left and right leg members 29 _(L) and 29 _(R)in correspondence to the lower support plates 98.

The left and right upper links 95 _(L) and 95 _(R) are turnablyconnected at their inner ends to opposite ends of the upper supportplates 97 through connecting pins 101, 101 having axes extending on thelongitudinal direction of the vehicle body frame structure F₁,respectively, and at their outer ends to the upper brackets 99 _(L) and99 _(R) through connecting pins 102, 102 having axes parallel to theconnecting pins 101, respectively.

The left and right lower links 96 _(L) and 96 _(R) are turnablyconnected at their inner ends to opposite ends of the lower supportplates 98 through connecting pins 103, 103 having axes parallel to theconnecting pins 101, 102, respectively, and at their outer ends to thelower brackets 100 _(L) and 100 _(R) through connecting pins 104, 104having axes parallel to the connecting pins 103, respectively.

In such parallel link arrangements 94 _(L) and 94 _(R), the left andright upper links 95 _(L) and 95 _(R) are independent from each other,and the left and right lower links 96 _(L) and 96 _(R) are independentfrom each other. Therefore, in this structure as it is, the parallellink arrangements 94 _(L) and 94 _(R) permit the upward and downwardmovement of the handle post 21 relative to the leg members 29 _(L) and29 _(R).

Therefore, the left and right lower links 96 _(L) and 96 _(R) areprovided with connecting frames 105 _(L) and 105 _(R), respectively, andthe connecting members 106, 106 are turnably connected at their oppositeends to the connecting frames 105 _(L) and 105 _(R), respectively.

Referring also to FIGS. 13 and 14, the connecting frame 105 _(L)provided on the left lower link 96 _(L) is formed into a substantiallytriangular shape by a rising pipe 107 _(L) integrally connected to theinner end of the left lower link 96 _(L) and extending upwards, and aconnecting pipe 108 _(L) connecting an intermediate portion of the leftlower link 96 _(L) and an upper portion of the rising pipe 107 _(L) toeach other. The connecting frame 105 _(R) provided on the right lowerlink 96 _(R) is formed into a substantially triangular shape by a risingpipe 107 _(R) integrally connected to the inner end of the right lowerlink 96 _(R) and extending upwards, and a connecting pipe 108 _(R)connecting an intermediate portion of the right lower link 96 _(R) andan upper portion of the rising pipe 107 _(R) to each other.

The connecting members 106, 106 are each formed of a band-shaped flatplate, and are disposed at a location where they sandwich the handlepost 21 from the front and the rear. The connecting members 106, 106 areturnably connected at their opposite ends to upper portions of therising pipes 107 _(L) and 107 _(R) of the connecting frames 105 _(L) and105 _(R) through connecting shafts 109, 109, respectively.

Such a simple structure in which the connecting members 106, 106 aremerely turnably connected at their opposite ends to the connecting frame105 _(L) provided on the left lower link 96 _(L) and to the connectingframe 105 _(R) provided on the right lower link 96 _(R), ensures thatthe handle post 21 cannot be permitted by the parallel link arrangements94 _(L) and 94 _(R) to be moved upwards and downwards relative to theleg members 29 _(L) and 29 _(R), and can withstand a load appliedthereto, whereby the function of the left and right parallel linkarrangements 94 _(L) and 94 _(R) can be maintained.

More specifically, as shown in FIG. 15, the leg members 29 _(L) and 29_(R) are inclined leftwards or rightwards with the leftward or rightwardinclination of the handle post 21, whereby the vehicle body framestructure F₁ can be inclined either leftwards or rightwards to enable abanking travel of the tricycle, leading to an enhanced steeringtravelability.

In the left parallel link arrangement 94 _(L), a left upright attitudemaintaining means 110 _(L) is provided between the handle post 21 andone of the left upper and lower links 95 _(L) and 96 _(L), e.g., theleft lower link 96 _(L). In the right parallel link arrangement 94 _(R),a right upright attitude maintaining means 110 _(R) is provided betweenthe handle post 21 and one of the right upper and lower links 95 _(R)and 96 _(R), e.g., the right lower link 96 _(R).

The left upright attitude maintaining means 110 _(L) includes a guidetube 111 which is secured to the handle post 21 and has an axisextending in a lateral direction and which is closed at its oppositeends by end wall members 112 _(L) and 112 _(R), respectively, a guiderod 113 which is secured at their opposite ends to the end wall members112 _(L) and 112 _(R) and concentrically disposed within the guide tube111, a movable tube 114 _(L) which is accommodated within the guide tube111 for sliding movement along the guide rod 113, a spring 115 forexhibiting a spring force in a direction to move the movable tube 114_(L) toward the end wall member 112 _(L), an abutment arm 117 _(L)provided on the movable tube 114 _(L) to protrude downwards from a slit116 _(L) provided in a left lower sidewall of the guide tube 111, and aroller 119 _(L) which is rotatably carried at an upper end of theconnecting frame 105 _(L) through a support shaft 118 _(L) having anaxis parallel to the connecting pins 101 to 104 and which is capable ofbeing put into abutment against the abutment arm 117 _(L) from theoutside in an axial direction of the guide tube 111.

The right upright attitude maintaining means 110 _(R) includes the guidetube 111, the guide rod 113 and the spring 115 commonly included in theleft upright attitude maintaining means 110 _(L), and further includes amovable tube 114 _(R) accommodated within the guide tube 111 for slidingmovement along the guide rod 113, an abutment arm 117 _(R) provided onthe movable tube 114 _(R) to protrude downwards from a slit 116 _(R)provided in a right lower sidewall of the guide tube 111, and a roller119 _(R) which is rotatably carried at an upper end of the connectingframe 105 _(R) through a support shaft 118 _(R) having an axis parallelto the support shaft 118 _(L) and which is capable of being put intoabutment against the abutment arm 117 _(R) from the outside in the axialdirection of the guide tube 111.

Collars 120 _(L) and 120 _(R) are secured to the movable tubes 114 _(L)and 114 _(R) with their outer peripheries in sliding contact with aninner surface of the guide tube 111, and the spring 115, which is a coilspring, is mounted under compression between both the collars 120 _(L)and 120 _(R) to surround the guide rod 113.

When the vehicle body frame structure F₁ has been inclined leftwards, asshown in FIG. 15, the abutment arm 117 _(L) and the movable tube 114_(L) in the left upright attitude maintaining means 110 _(L) are pushedrightwards by the roller 119 _(L), while compressing the spring 115.During this time, in the right upright attitude maintaining means 110_(R), the movable tube 114 _(R) is in abutment against the end wallmember 112 _(L), and the roller 119 _(R) is spaced apart from theabutment arm 117 _(R). Therefore, the spring force for returning thehandle post 21 to the upright attitude is applied from the left uprightattitude maintaining means 110 _(L) to the handle post 21 through theguide tube 111, and the right upright attitude maintaining means 110_(R) cannot exert the spring force to the handle post 21. On the otherhand, when the handle post 21 has been inclined rightwards from theupright attitude, the spring force for returning the handle post 21 tothe upright attitude is applied from the right upright attitudemaintaining means 110 _(R) to the handle post 21 through the guide tube111, and the left upright attitude maintaining means 110 _(L) cannotexert the spring force to the handle post 21.

Even in the second embodiment, an effect similar to that in the firstembodiment can be provided.

FIGS. 16 and 17 show a third embodiment of the present invention.

A vehicle body frame structure F₂ in a tricycle used also as a cart iscomprised of a handle post 21 (see the first and second embodiments; andwhich is not shown in FIGS. 16 and 17), a saddle post 22, a rear frame121, a bottom pipe 24 and a link pipe 122. The vehicle body framestructure F₂ is capable of being switched over between a bicycle mode inwhich it has been deployed, as shown in FIG. 16, and a cart mode inwhich it has been folded up, as shown in FIG. 17.

The rear frame 121 is comprised of the following members connectedintegrally with one another: a tube 61 which rotatably supports crankpedals 65, 65, a first pipe frame 123 extending in a forward lowerinclined manner from the tube 61 in the bicycle mode, a second pipeframe 124 extending in a forward upper inclined manner from the tube 61in the bicycle mode, a rear fork 62 which extends in a rearward lowerinclined manner from the tube 61 in the bicycle mode and on a rear endof which a rear wheel W_(R) is supported by a shaft, and a reinforcingpipe 125 which connects an upper end of the second pipe frame 124 and anintermediate portion of the rear fork 62 to each other.

The bottom pipe 24 is turnably connected at its one end to a bracket 71mounted at a lower portion of the handle post 21 through a pivot 72having an axis parallel to a rotational axis of the rear wheel W_(R),and a lower end of the saddle post 22, the other end of the bottom pipe24 and a tip end of the first pipe frame 124 in the rear frame 121 areconnected together through a pivot 126 parallel to the pivot 72.

The link pipe 122 connects an intermediate portion in the upward anddownward direction of the handle post 21 and a lengthwise intermediateportion of the saddle post 22 to each other. The link pipe 122 isconnected at its one end to a bracket 127 secured to the intermediateportion in the upward and downward direction of the handle post 21through a pivot 128 having an axis parallel to the pivots 73 and 126,and at the other end to a bracket 129 secured to the lengthwiseintermediate portion of the saddle post 22 through a pivot 130 having anaxis parallel to the pivot 128.

The handle post 21, the saddle post 22, the rear frame 121, the bottompipe 24 and the link pipe 122, which are turnably connected to oneanother through the pivots 72, 126, 128 and 130 to form the vehicle bodyframe structure F₂, comprise a link mechanism which is capable ofswitching over, from one to another, the bicycle mode in which thevehicle frame body structure F₂ has been deployed, so that both of leftand right front wheels W_(FL) and W_(FR) and the rear wheel W_(R) havebeen grounded to provide the maximum wheel base, as shown in FIG. 16,and the cart mode in which the vehicle frame body structure F₂ has beenfolded up, so that the rear wheel W_(R) spaced apart from the groundsurface has been inserted between the left and right front wheels W_(FL)and W_(FR) which are in their grounded states, as shown in FIG. 17.

When the vehicle frame body structure F₂ is in the bicycle mode, thebicycle mode of the vehicle frame body structure F₂ can be maintained bylocking means 131 and 132.

The locking means 131 is provided between the saddle post 22 and therear frame 121 among the handle post 21, the saddle post 22, the rearframe 121, the bottom pipe 24 and the link pipe 122 which form thevehicle body frame structure F₂.

The locking means 131 includes a resilient member 133 which is made ofan elastic material, e.g., a rubber and which is fixed to the rear frame121 in such a manner that it is sandwiched between the saddle post 22and the rear frame 121, when the vehicle body frame structure F₂ is inthe bicycle mode, and an engage member 135 which is mounted to the rearframe 121 to maintain the relative positions of the saddle post 22 andthe rear frame 121 so as to releasably engage a locking member 134mounted on the saddle post 22.

The resilient member 133 is secured to upper ends of the second pipeframe portion 124 and the reinforcing pipe 125 in the rear frame 121,and is sandwiched between the saddle post 22 and the rear frame 121 toexhibit a resilient force opposing a riding load applied from the saddlepost 22, when the vehicle body frame structure F₂ is in the bicyclemode.

The locking means 132 is provided between the bottom pipe 24 and thesaddle post 22 among the handle post 21, the saddle post 22, the rearframe 121, the bottom pipe 24 and the link pipe 122 which form thevehicle body frame structure F₂.

The locking means 132 includes a resilient member 136 which is made ofan elastic material, e.g., a rubber and which is fixed to the bottompipe 24 in such a manner that it is sandwiched between the bottom frame24 and the saddle post 22, when the vehicle body frame structure F₂ isin the bicycle mode, and an engage member 138 which is mounted to thesaddle post 22 to maintain the relative positions of the saddle post 22and the bottom pipe 24 so as to releasably engage the bottom pipe 24. Asupport arm 137 is integrally connected to the bottom pipe 24 in such amanner that a tip end thereof is opposed to a front surface of thesaddle post 22 in the bicycle mode, and the resilient member 136 isfixed to the tip end of the support arm 137 in such a manner that itengages the front surface of the saddle post 22. Thus,when the vehiclebody frame structure F₂ is in the bicycle mode, the resilient member 136is sandwiched between the support arm 137 and the saddle post 22 toexhibit the resilient force opposing the riding load.

The engage member 138 is mounted to the saddle post 22, so that itengages the tip end of the support arm 137, when the vehicle body framestructure F₂ is in the bicycle mode.

In the first and second embodiments, the handle post 21, the saddle post22, the rear frame 23, the bottom pipe 24, the first link pipe 25 andthe second link pipe 26 are turnably connected together through theseven pivots 69, 72, 73, 75, 77, 79 and 81 to form the vehicle bodyframe structure F₁, and on the other hand, in the third embodiment, thehandle post 21, the saddle post 22, the rear frame 121, the bottom pipe24 and the link pipe 122 are turnably connected together through thefour pivots 72, 126, 128 and 130 to form the vehicle body framestructure F₂, whereby the arrangement of the vehicle body framestructure F₂ can be simplified.

FIGS. 18 to 20 show a fourth embodiment of the present invention.

The attitude of a vehicle body frame structure F₂ when in a bicycle modeis maintained by first and second locking means 141 and 142. The firstlocking means 141 is provided between a saddle post 22 and a rear frame121 of the components of a vehicle body frame structure F₂, and thesecond locking means 142 is provided between a bottom pipe 24 and thesaddle post 22.

The first locking means 141 includes a resilient member 133 which ismade of an elastic material, e.g., a rubber and which is fixed to therear frame 121 in such a manner that it is sandwiched between the saddlepost 22 and the rear frame 121, when the vehicle body frame structure F₂is in the bicycle mode, a lever 143 turnably mounted to the saddle post22, a hook 145 which is secured to the rear frame 121 to maintain therelative positions of the saddle post 22 and the rear frame 121 so as toreleasably engage a locking pin 144 mounted at one end of the lever 143,and a torsion spring 146 mounted between the lever 143 and the saddlepost 22 to exhibit a spring force for biasing the lever 143 in adirection to bring the locking pin 144 of the lever 143 into engagementwith the hook 145.

The resilient member 133 is secured to the upper ends of the second pipeframe 124 and the reinforcing pipe 125 in the rear frame 121, and issandwiched between the saddle post 22 and the rear frame 121 to exhibita resilient force opposing a riding load applied from the saddle post 22when the vehicle body frame structure F₂ is in the bicycle mode.

The second locking means 142 includes a resilient member 136 fixed to atip end of a support arm 137 integrally connected to the bottom pipe 24,and an operating lever 148 turnably mounted to the saddle post 22, sothat it can be brought into engagement with a locking pin 147 fixedlymounted on the support arm 137. When the vehicle body frame structure F₂is in the bicycle mode, the resilient member 136 is sandwiched betweenthe bottom frame 24 and the saddle post 22 by bringing the operatinglever 148 into engagement with the locking pin 147, whereby the relativepositions of the saddle post 22 and the bottom pipe 24 are maintained.

The operating lever 148 is integrally provided with the followingportions as shown in FIG. 20: a flat plate portion 148a having a supportbore 150 which is provided therein and through which a support shaft 149for turnably mounting the operating lever 148 to the saddle post 22 isinserted, an engage portion 148 b which protrudes from an outer edge ofthe flat plate portion 148 a toward the support arm 137, so that it canbe brought into engagement with the locking pin 147, a first operatingportion 148 c which protrudes from the outer edge of the flat plateportion 148 a in a direction opposite from the engage portion 148 b toturn the operating lever 148 in a clockwise direction as viewed in FIG.19 by applying a force from the above to bring the engage portion 148 binto engagement with the locking pin 147, and a second operating portion148 d which protrudes from the outer edge of the flat plate portion 148a in the direction opposite from the engage portion 148 b to turn theoperating lever 148 in a counterclockwise direction as viewed in FIG. 19by applying a force from the above to release the engagement of theengage portion 148 b with the locking pin 147.

The operating lever 148 can be turned in the clockwise direction asviewed in FIG. 19 from an opened position P₀ via a tight position P_(T)to a locked position P_(L). The engage portion 148 b is formed into anarcuate shape such that the distance from an axis of the support shaft149 is gradually decreased as the operating lever 148 is turned in thecounterclockwise direction as viewed in FIG. 19, so that the engagementof the engage portion 148 b with the locking pin 147 is started inresponse to the turning movement of the operating lever 148 from theopened position P₀ to the tight position P_(T), and the locking pin 147is pulled nearer to gradually compress the resilient member 136, as theoperating lever 148 is turned about the support shaft 149 in theclockwise direction as viewed in FIG. 19 from the tight position P_(T)to the locked position P_(L).

When an operating force has been applied to the first operating portion148 c to turn the operating lever 148 to the locked position P_(L), thelocking pin 147 and the engage portion 148 b are brought into frictionengagement with each other by the large resilient force exhibited by theresilient member 136 and thus, the operating lever 148 is stopped at thelocked position P_(L), unless the operating force is applied to theoperating lever 148.

An elongated bore 151 having an arcuate shape about the axis of thesupport shaft 149 is provided in the flat plate portion 148 a of theoperating lever 148. On the other hand, a connecting rod 152 is turnablyconnected at its upper end to the other end of the lever 143 in thefirst lock means 141 and extends downwards, with a lower end of theconnecting rod 152 being engaged in the elongated bore 151. The lengthof the connecting rod 152 is set, so that when the operating lever 148of the second lock means 142 is in the locked position P_(L) when thefirst lock means 141 is in the locked state, a lower end of theconnecting rod 152 is in a position corresponding to an upper end of theelongated bore 151, so that the unlocking of the first lock means 141 isimpossible, and when the operating lever 148 of the second lock means142 is in the tight position P_(T) with the first lock means 141 beingin the locked state, the lower end of the connecting rod 152 is in aposition corresponding to a lower end of the elongated bore 151, so thatthe unlocking of the first lock means 141 is possible, and further, whenthe operating lever 148 of the second lock means 142 has been turned tothe opened position P₀, the lever 143 is pushed upwards against thespring force of the torsion spring 146 to forcibly unlock the first lockmeans 141.

According to the fourth embodiment, the first lock means 141 providedbetween the saddle post 22 and the rear frame 121 of the components ofthe vehicle body frame structure F₂ and the second lock means 142provided between the bottom pipe 24 and the saddle post 22 areoperatively connected to each other, so that the locked state of thefirst lock means 141 can be maintained in response to the lockingoperation of the second lock means 142, and the first lock means 141 canbe unlocked in response to the unlocking operation of the second lockmeans 142.

Therefore, it is necessary to maintain the relative positions of thesaddle post 22 and the rear frame 121 as well as between the bottom pipe24 and the saddle post 22 in the bicycle mode, due to the vehicle bodyframe structure F₂ being of a simple arrangement comprising the handlepost 21, the saddle post 22, the rear frame 121, the bottom pipe 24 andthe link pipe 122 which are turnably connected together through fourpivots 72, 126, 128 and 130, as described above. However, in response tothe locking operation of the second lock means 142 of the first andsecond lock means 141 and 142, the first lock means 141 is alsomaintained in the locked state, and in response to the unlockingoperation of the second lock means 142, the first lock means 141 isunlocked, whereby the locking operation and the unlocking operation canbe facilitated extremely.

Although the embodiments of the present invention have been described indetail, it will be understood that the present invention is not limitedto the above-described embodiments, and various modifications in designmay be made without departing from the spirit and scope of the inventiondefined in claims.

For example, the present invention has been described as applied to thetricycle used also as the cart in each of the embodiments, but thepresent invention is applicable to a tricycle which is not used as acart. The present invention is also applicable not only to a tricycledriven by a human power, but also to a tricycle including a powersource, or a tricycle including a power source assisted by a humanpower.

What is claimed is:
 1. A tricycle including a pair of left and rightfront steerable wheels (W_(FL), W_(FR)) supported at a front portion ofa vehicle body frame structure (F₁), and a single rear drivable wheel(W_(R)) supported at a rear portion of the vehicle body frame structure(F₁), wherein said tricycle comprises a cylindrical handle post (21)which is fixedly mounted at a front end of said vehicle body framestructure (F₁) and which turnably supports a steering shaft (27)connected to a steering handlebar (28), left and right upper links (38_(L), 38 _(R)) which are integrally connected to each other andpivotally supported at an upper end of said handle post (21), left andright lower links (39 _(L), 39 _(R)) which are integrally connected toeach other and pivotally supported at a lower end of said handle post(21), a cylindrical left leg member (29 _(L)) which is pivotallysupported at upper and lower opposite ends thereof to outer ends of saidleft upper and lower links (38 _(L), 39 _(L)), a cylindrical right legmember (29 _(R)) which is pivotally supported at upper and loweropposite ends thereof to outer ends of said right upper and lower links(38 _(R), 39 _(R)), a left front wheel support member (30 _(L))rotatably supported on said left leg member (29 _(L)), a right frontwheel support member (30 _(R)) rotatably supported on said right legmember (29 _(R)) , said left front wheel (W_(FL)) being supported onsaid left front wheel support member (30 _(L)) and disposed immediatelybelow said left leg member (29 _(L)), said right front wheel (W_(FR))being supported on said right front wheel support member (30 _(R)) anddisposed immediately below said right leg member (29 _(R)), and asteering operatively-connecting means (31 to 34) being disposed belowsaid handle post (21) and both said leg members (29 _(L), 29 _(R)) foroperatively connecting said steering shaft (27) and said left and rightfront wheel support members (30 _(L), 30 _(R)) to each other.
 2. Atricycle including a pair of left and right front steerable wheels(W_(FL), W_(FR)) supported at a front portion of a vehicle body framestructure (F₂), and a single rear drivable wheel (W_(R)) supported at arear portion of the vehicle body frame structure (F₂), wherein saidtricycle comprises a cylindrical handle post (21) which is fixedlymounted at a front end of said vehicle body frame structure (F₂) andwhich turnably supports a steering shaft (27) connected to a steeringhandlebar (28) left and right upper links (95 _(L), 95 _(R)) which areindependent from each other and pivotally supported at an upper end ofsaid handle post (21), left and right lower links (96 _(L), 96 _(R))which are independent from each other and pivotally supported at a lowerend of said handle post (21), a cylindrical left leg member (29 _(L))which is pivotally supported at upper and lower opposite ends thereof toouter ends of said left upper and lower links (95 _(L), 96 _(L)), acylindrical right leg member (29 _(R)) which is pivotally supported atupper and lower opposite ends thereof to outer ends of said right upperand lower links (95 _(R), 96 _(R)), a left front wheel support member(30 _(L)) turnably supported on said left leg member (29 _(L)), a rightfront wheel support member (30 _(R)) turnably supported on said rightleg member (29 _(R)), left and right connecting frames (105 _(L), 105_(R)) which are fixedly mounted on at least ones of: said left and rightupper links (95 _(L), 95 _(R)); and said left and right lower links (96_(L), 96 _(R)), respectively, a connecting member (106) which isturnably connected at opposite ends thereof to said connecting frames(105 _(L), 105 _(R)), said left front wheel (W_(FL)) being supported onsaid left front wheel support member (30 _(L)) and disposed immediatelybelow said left leg member (29 _(L)), said right front wheel (W_(FR))being supported on said right front wheel support member (30 _(R)) anddisposed immediately below said right leg member (29 _(R)), and asteering operatively-connecting means (30 to 34) being disposed belowsaid handle post (21) and both said leg members (29 _(L), 29 _(R)) foroperatively connecting said steering shaft (27) and said left and rightfront wheel support members (30 _(L), 30 _(R)) to each other.
 3. Atricycle according to claim 1 or 2, further including a left uprightattitude maintaining means (44 _(L), 110 _(L)) which is provided betweensaid handle post (21) and one of said left upper and lower links (38_(L), 39 _(L), 95 _(L), 96 _(L),) for exhibiting a spring force forreturning said handle post (21) to upright attitude thereof in responseto said handle post (21) inclining leftwards from the upright attitude,but for avoiding exhibiting a spring force, when said handle post (21)is inclined rightwards from the upright attitude, and a right uprightattitude maintaining means (44 _(R), 110 _(R),) which is providedbetween said handle post (21) and one of the right upper and lower links(38 _(R), 39 _(R), 95 _(R), 96 _(R),) for exhibiting a spring force forreturning said handle post (21) top upright attitude thereof in responseto said handle post (21) inclining rightwards from the upright attitude,but for avoiding exhibiting a spring force, when said handle post (21)is inclined leftwards from the upright attitude, and a spring force forbiasing said handle post (21) in the direction toward the uprightattitude being applied to said left and right upright attitudemaintaining means (44 _(L), 110 _(L), 44 _(R), 110 _(R),) even in theupright state of said handle post (21), wherein said left and rightupright attitude maintaining means maintain said tricycle in an uprightmanner.